Oparin and Haldane hypothesis



Chemical and physical processes combine to make cells


  • Early earth had water vapor and compounds from volcanic eruptions (CO2, CH4, NH3)
    • atmosphere was reducing (now controversial)
    • energy from UV or lightning
    • oceans = primordial soup of organic molecules

Miller & Urey experiments: Testing Oparin & Haldane


Fossils are biased


Fossils trace the steps of animal evolution


Progression of life on earth



  • Fossils help divide geologic record into 4 eons
  1. Hadean
  2. Archaen
  3. Proterozoic


4. Phanerozoic: last 500 million years


  • Recent geologic ages (3), each with unique animal life
  1. Paleozoic
  2. Mesozoic
  3. Cenozoic

Review: Evolution of Eukaryotes and the Great Oxygenation


Early animal life and the Cambrian explosion




  • 2nd oxygen revolution tied to evolution of animals


  • Prior to Cambrian all large animals had soft body
    • little evidence of predation
    • grazers, scavengers, filter feeders


  • Large predators evolve in early Cambrian
    • 545-525 mya
    • predator vs prey evolution
    • evolution of eyes

Cambrian explosion = bizarre aquatic creatures



  • Spectacular diversification of animals


  • Abrupt period: only 10-20 million years!
    • troubled Darwin


  • Hard skeletons and soft bodies
    • diverse body morphology (Hox genes)


  • Bilaterally symmetrical animals
    • possible formation of ‘head’ region
    • organized sensory organs

Burgess Shale



  • British Columbia’s Yoho National Park
    • 60,000 unique fossils
    • one of the most diverse and well-preserved fossil sites


  • Creatures from the Cambrian explosion
    • origins dating 545 to 525 million years ago


  • Mudslides from barren land buried marine organisms
    • sediment deposited in deep-water basin next to enormous algal reef
    • soft and hard body fossils

Nearly all major animal groups in Burgess Shale!!!


Geologic history of plants and animals on land


Animal colonization of land



  • Arthropods (insects/spiders): 450 mya


  • Tetrapods: 350 mya
    • evolved from lobe-finned fishes

Rise and fall of animal diversity



  • Diversification is not a smooth process


  • Speciation rates: how many species in a lineage are created


  • Extinction rates: how many species in a lineage are lost


  • The fate of a lineage depends on this rise and fall
    • plate tectonics
    • mass extinctions
    • adaptive radiations


  • Example: first tetrapods → dinosaurs → mammals

Continental Drift



  • Continents = floating plates of Earth’s crust
    • plate movement = continental drift
    • a few cm a year


  • Landmasses came together 3 times over last billion years
    • yields new continents
    • new super continent in ~250 million years


  • Mountains and islands form at boundaries
    • Indian + Eurasia = Himalayan Mtn (45 mya)

Continental Drift…. so what?




  • Landmass change alters livable habitats
    • species distributions change
    • oceans change (Valley of Whales)
    • Pangaea (250 mya) drained shallow oceans


  • Landmass change alters climate
    • Canada was once tropical


  • Continental drift drives speciation
    • adapt, move or die

Allopatric speciation: Australian marsupials


Mass Extinctions


  • 5 mass extinctions in fossil record
    • 50% of marine species extinct


  • Permian extinction: 96% marine loss
    • most recent: Cretaceous (bye bye Dino)


  • Causes are varied
    • volcanoes & meteors
    • massive climate change
    • ocean chemistry


  • Evolution favors innovation but…
    • innovations can be wiped out
    • What if early primates went extinct?

Adaptive Radiation



  • Define:


  • Occur on large scale after extinction events
    • many vacant habitats
    • favors evolutionary innovations


  • Innovation leads to diversification


  • Dinosaur extinction → mammals
    • small and nocturnal → …

Regional Adaptive Radiation: Hawaiian islands born ‘naked’